1. Field of the Invention
This invention relates to a chaining thread sew-in device installed in an overlock sewing machine, which is used to cut the chaining thread formed consecutively with the seams formed on a cloth when an edge of the cloth is overedged by the overlock sewing machine, by leaving a specified length from the sewing machine side, and to sew the chaining thread consecutive into the seams on the next cloth from the sewing machine side.
2. Description of the Prior Art
A conventional chaining thread sew-in device mounted on an overlock sewing machine was effected by: installing a chaining thread holder/cutter composed of a cutter and a pinching member made of an elastic material on the working face on the operator side of the needle drop point of the sewing machine cutting a chaining thread brought to the operator side of the sewing machine by the operator together with the cloth when sewing is finished and pressed against the cutter, by pinching a free end of the cut chaining thread by the pinching member so as to hold the chaining thread left on the sewing machine side on a throat plate of the machine and by preventing loosening of seams at the starting point of sewing without conducting specific bar tacking by sewing the chaining thread into the seams of the next cloth.
In such a chaining thread sew-in device, however, the operator moved the cloth to the operator side of the needle drop point every time the sewing of a cloth was finished in order to cut the chaining thread formed consecutively to the cloth, and therefore the working efficiency could not be improved or the operation could not be automated.
To solve the above problems, proposed in U.S. Pat. No. 4,149,478 was a chaining thread sew-in device. To suck a chaining thread linked to the seams formed on a cloth into a suction tube on the back side of a needle drop point; to cut the chaining thread by a cutter installed in an opening of the suction tube for leaving a specified length from the sewing machine side; to move a free end of the chaining thread linked to the sewing machine side to the operator side of the needle drop point by air pressure; to suck the free end of the chaining thread moved in this way into a chaining thread free end suction part; and to pinch the free end of the chaining thread by actuating a chaining thread pinching part installed in the working face of the cloth plate.
The conventional apparatus represented by the one disclosed in the above U.S. Pat. No. 4,149,478 was designed to dispose the chaining thread pinching part and the free end suction part of the chaining thread on the working face of the machine, and as a result, the chaining thread pinching part disturbs the cloth feeding thereby reducing the working efficiency of the machine.
Besides, in the apparatus with a strong pinching force of the chaining thread in the chaining thread pinching part, when sewing the chaining thread, the free end of which is pinched into the seams on the next cloth, the edge of the cloth is pulled by the chaining thread and curled downward.
Another problem in the conventional device was that, as the length of chaining thread sewn into the seams of the cloth was determined by the cutting position of the cutter installed in the opening of the suction tube, it was difficult to change the length of the chaining thread to be sewn in dependence on the product.
Other known technologies about the present invention aside from the one in U.S. Pat. No. 4,149,479, are disclosed in U.S. Pat. Nos. 4,187,793, 4,220,150, 4,644,884 and 4,679,515.